involuntaries need help

Ive been using different model Aneros for 2+ years. I use them on and off, sometimes 2x week sometimes once every other week. I have some questions and want advice.

Twice Ive had nice involuntaries going and it felt REALLY good, my question is, how do I let the aneros do its thing and still contract? These to actions seem the opposite of one another? can someone explain?

Usually, I have laid back and let the aneros do all the work. I want to get some CRAZY involuntaries going again!

Yes, Im enjoying the journey. Ive tried many lubes and found Probe thick and rich the best for me.

Also, Is it best to think about fantasies or be somewhere not concentrating on the aneros?

Any advice is apprecciating.

PS: When I first started I used the Hynoaneros MP3 and would get this rush of energy building in the plevic area that flowed up to my chest. I havent had this in a while, anyone else experience this and has it appeared then disappeared?

Thanks guys!